1. Field of the Invention
This invention generally relates to the diagnosis and treatment of strictures in biliary ducts and urinary or pancreatic tracts and more particularly to apparatus that is useful in such diagnoses and treatment.
2. Description of Related Art
If a stricture forms in an individual's biliary duct, urinary tract or pancreatic tract, flow through the duct or tract can stop. One step used in the diagnosis and treatment of symptoms resulting from such a stricture is a determination of whether the cells in the stricture are malignant. One methodology for diagnosing such malignancy involves brush cytology performed for example, by a cytology brush apparatus as described in U.S. Pat. No. 4,763,670. Thereafter the physician may place a stent in the vessel to open or dilate the stricture. Apparatus for placing such a stent is described in U.S. Pat. No. 5,234,457.
During the diagnosis and treatment of a stricture in the biliary duct, urinary and pancreatic tracts, a physician initially introduces an endoscope with viewing and working channels through various vessels to position the distal end of the endoscope closely adjacent the proximal side of the stricture. In this discussion the phrases "proximal" and "distal" are applied in terms of the apparatus and the physician. Consequently the proximal end of the apparatus is located externally of the patient for direct manipulation by the physician. Next the physician may perform endoscopic retrograde cholangiopancreatography (ERCP) or transhepatic cholangiography (THC) in the biliary tree or retrograde cystography in the urinary tract. The physician may, prior to or during such procedures, locate the stricture by the injection of contrast media. In addition, the physician may advance an ERCP cannula or similar catheter-like device through the stricture either over a previously placed guidewire or independently of a guidewire.
U.S. Pat. No. 4,763,670 discloses a cytology brush apparatus that is adapted for being advanced through the working channel of an endoscope. This apparatus has a single lumen that receives a standard cytology brush. Consequently the physician must remove any previously located cannula and guidewire from the stricture before using the cytology brush apparatus. Removing the cannula or guidewire has the undesired effect of eliminating any dilation through the stricture that the guidewire has achieved, often only after an extended time and completion of a tedious procedure. It therefore becomes necessary to advance the cytology brush at least partially through the stricture to obtain a sample at an appropriate location without the benefit of any access that the guidewire had established.
Alternatively it might be possible to lead a catheter-like device partially through the stricture over a guidewire that extends through the stricture then remove the guidewire to allow a cytology brush to be transported through the catheter-like device. However, to regain whatever access the catheter-like device has preserved, the cytology brush must be retracted through the length of the catheter device so the guidewire can be reintroduced. Withdrawing a cytology brush through the length of such a catheter-like device can deposit all or most of the sample on the interior surface of the catheter-like device. Consequently physicians normally will withdraw the guidewire, use the cytology brush apparatus, remove the cytology brush apparatus with the catheter-like device and then reintroduce the guidewire through the stricture.
The length of any stent used to dilate a stricture should correspond closely to the length of the stricture. A physician currently views a two-dimensional image of the stricture obtained by fluoroscopy or X-ray imaging and will use the imaged endoscope to estimate the stricture length. If the stricture lies entirely in the plane of the image, this process provides a reasonably accurate estimate of stricture length. However, in most cases the stricture does not lie in the plane of the image, so any such estimate will be incorrect. Consequently physicians tend to estimate length based upon information obtained by scaling an image and intuitive knowledge of the anatomy. This usually results in placing a stent that is longer than necessary.
After the guidewire has been reintroduced and a stent of appropriate length has been selected, the physician introduces a stent delivery system such as is disclosed in U.S. Pat. No. 5,234,457, over the guidewire and into the stricture. Once located, the stent expands and dilates the stricture. Next the physician can remove the stent delivery system, the guidewire and the endoscope to complete the procedure.
As previously indicated, this procedure has several disadvantages that can be summarized as follows. The guidewire must be removed during the various procedures thereby losing any access through stricture. The procedure incorporates several steps that can prolong the procedures. The selection of stent length is imprecise.
U.S. Pat. Nos. 4,235,244, 4,850,957, 4,966,162 and 5,217,023 disclose other prior art cytology brush apparatus for obtaining samples through the working channel of an endoscope. Each of these patents discloses a cytology brush with a plug of water-soluble material that closes a distal end of an outer catheter body to prevent contamination of an inner cavity body and the brush during its introduction into the body. U.S. Pat. No. 4,235,244 obtains a sample on the ends of the bristle brushes that are withdrawn into a protective sheath. U.S. Pat. Nos. 4,850,957 and 4,966,162 and 5,217,023 flush recovered samples debrided from tissue by a brush. None of these cytology brushes discloses any structure for enabling cytology brush apparatus to be used in conjunction with a guidewire or any method for estimating stent length. Consequently each cytology brush apparatus disclosed in these patents introduces the same complexities and operates with the same disadvantages as previously indicated.
U.S. Pat. Nos. 3,613,664 and 4,946,440 disclose cytology brushes with self-contained steerable guidewires while U.S. Pat. Nos. 4,227,537 and 4,662,381 disclose cytology brushes that are self-contained primarily for collecting samples from the cervix. None of these patents, other than U.S. Pat. No. 4,946,440, discloses any use in the diagnosis and treatment of strictures in the biliary duct or the pancreatic or urinary tracts. None is adapted for use with a standard guidewire. U.S. Pat. Nos. 3,613,664 and 4,662,381 and 4,946,440 also do not disclose or suggest any structure for estimating stent length requirements.
U.S. Pat. No. 4,227,537 discloses a brush apparatus for collecting sample tissue from an endometrial cavity to aid in diagnosing endometrial cancer. The apparatus includes a catheter-like device with a graded scale that allows a physician to determine the location of each sample with respect to some reference point. However, this patent does not disclose or suggest any method for estimating the length of a stricture with particular reference to determining stent length.
U.S. Pat. No. 5,201,323 discloses a wire-guided cytology brush that has a flexible outer sheath with a lumen for accepting a flexible inner sheath. A brush or similar tissue gathering device is located at the distal end of the inner sheath. The inner sheath has a lumen therethrough for passing over a guidewire. First and second handles at the proximal ends of the inner and outer sheaths manipulate the inner and outer sheaths respectively. A retainer clip maintains the relative positioning of the inner sheath within the outer sheath during insertion and removal of the brush assembly over the guidewire.
This apparatus does permit a physician to obtain tissue samples from within a stricture without having to remove a guidewire. However, the path of any cytology brush apparatus, including the cytology brush shown in this patent, is a tortuous path. At each of various bends along the path, the guidewire and inner sheath come into contact and produce friction during relative movement between the inner sheath and guidewire. Thus if a physician holds the outer sheath handle in a fixed position with one hand while manipulating the inner sheath with the other, it is possible for the movement of the inner sheath to move the guidewire. Any such motion should be avoided. Moreover, the requirement of removing and reinstalling the retainer clip before and after a sample is taken further complicates the physician's procedure.